NCA, NCM811, and the Route to Ni-Richer Lithium-Ion Batteries

Systematic study of Co-free LiNi0.9Mn0.07Al0.03O2 Ni-rich cathode materials to realize high-energy density Li-ion batteries

The growing use of EVs and society's energy needs require safe, affordable, durable, and eco-friendly high-energy lithium-ion batteries (LIBs). To this end, we synthesized and investigated the removal of Co from Al-doped Ni-rich cathode materials, specifically LiNi0.9Co0.1Al0.0O2 (NCA-0), LiNi0.9Mn0.1Al0.0O2 (NMA-0), LiNi0.9Mn0.07Al0.03O2 (NMA-3), intending to enhance LIB performance and reduce the reliance on cobalt, a costly and scarce resource. Our study primarily focuses on how the removal of Co affects the material characteristics of Ni-rich cathode material and further introduces aluminum into the cathode composition to study its impacts on electrochemical properties and overall performance. Among the synthesized samples, we discovered that the NMA-3 sample, modified with 3 mol% of Al, exhibited superior battery performance, demonstrating the effectiveness of aluminum in promoting cathode stability. Furthermore, the Al-modified cathode showed promising cycle life under normal and high-temperature conditions. Our NMA-3 demonstrated remarkable capacity retention of ∼ 88 % at 25 °C and ∼ 81 % at 45 °C after 200 cycles at 1C, within a voltage range of 2.8-4.3 V, closely matching the performances of conventional NCM and NCA cathodes. Without cobalt, the cathodes exhibited increased cation disorder leading to inferior rate capabilities at high C-rates. In-situ transmission XRD analysis revealed that the introduction of Al has reduced the phase change and provided much-needed stability to the overall structure of the Co-free NMA-3. Altogether, the findings suggest that our aluminum-modified NMA-3 sample offers a promising approach to developing Co-free, Ni-rich cathodes, effectively paving the way toward sustainable, high-energy-density LIBs.

Electrolyte Engineering Toward High Performance High Nickel (Ni ≥ 80%) Lithium-Ion Batteries

High nickel (Ni ≥ 80%) lithium-ion batteries (LIBs) with high specific energy are one of the most important technical routes to resolve the growing endurance anxieties. However, because of their extremely aggressive chemistries, high-Ni (Ni ≥ 80%) LIBs suffer from poor cycle life and safety performance, which hinder their large-scale commercial applications. Among varied strategies, electrolyte engineering is very powerful to simultaneously enhance the cycle life and safety of high-Ni (Ni ≥ 80%) LIBs. In this review, the pivotal challenges faced by high-Ni oxide cathodes and conventional LiPF6 -carbonate-based electrolytes are comprehensively summarized. Then, the functional additives design guidelines for LiPF6 -carbonate -based electrolytes and the design principles of high voltage resistance/high safety novel electrolytes are systematically elaborated to resolve these pivotal challenges. Moreover, the proposed thermal runaway mechanisms of high-Ni (Ni ≥ 80%) LIBs are also reviewed to provide useful perspectives for the design of high-safety electrolytes. Finally, the potential research directions of electrolyte engineering toward high-performance high-Ni (Ni ≥ 80%) LIBs are provided. This review will have an important impact on electrolyte innovation as well as the commercial evolution of high-Ni (Ni ≥ 80%) LIBs, and also will be significant to breakthrough the energy density ceiling of LIBs.

Durable lithium-ion insertion/extraction and migration behavior of LiF-encapsulated cobalt-free lithium-rich manganese-based layered oxide cathode

Lithium-rich manganese-based cathode has made a subject of intense scrutiny for scientists and application researchers due to their exceptional thermal stability, high specific capacity, high operating voltage, and cost-effectiveness. However, the inclusion of cobalt, as a crucial component in lithium-rich manganese-based cathode materials, has become a cause for concern due to its limited availability and non-renewable nature, which eventually limits the growth of the battery industry and increase costs. Considering the poor stability of cobalt-free cathode, this work proposes a coating strategy of LiF through a simple high-temperature melting method. Directly coating LiF on Li1.2Ni0.2Mn0.6O2 surface is found to be an effective way to protect the cathode material, decrease metal solubility, and inhibit irreversible phase transition processes, thus leading to an improved electrochemical performance. As a result, the battery employing LiF coated Li1.2Ni0.2Mn0.6O2 cathode can be stabilized over 280 cycles and maintain a capacity of 110 mAh g-1 at 1C. What's more, the mechanisms of ion insertion/extraction behavior and ion migration process are also studied systematically. This study will open the avenue to develop a high-energy battery system with cobalt-free cathode.

Revealing Phase Transition in Ni-Rich Cathodes via a Nondestructive Entropymetry Method

With the expanding requirements of recent energy regulations and economic interest in high-performance batteries, the need to improve battery energy density and safety has gained prominence. High-energy-density lithium batteries, employed in next-generation energy storage devices, rely on nickel-rich cathode materials. Since they have extremely high charge/discharge capacity, high operating voltage, prolonged cycle life, and lower cost, nickel-rich cathode materials such as Ni-rich NCM (LiNix > 0.8CoyMnzO2) and Ni-rich NCA (LiNix > 0.8CoyAlzO2) are of particular interest to researchers. Several in situ characterization methodologies are currently used to understand lithium-ion battery electrode response and deterioration better. Nevertheless, in many contexts, these measurement methodologies must be combined with specially designed cells and electrode materials with distinct forms, which is sometimes inconvenient. As an alternative, thermo-voltammetric dynamic characterization may be utilized to describe the thermal internal characteristics of various electrode materials, such as the structural changes and electrode reactions that occur during charging and discharging. In this paper, a nondestructive entropy measurement method demonstrates that phase change occurs for NCM (LiNi0.83Co0.12Mn0.05O2) and NCA (LiNi0.88Co0.09Al0.03O2) at 40-30% of state of charge (SOC) and 90-80% of SOC, respectively. This is confirmed by ex situ X-ray diffraction (XRD) measurements for these highly popular cathodes.

Tailored PVDF Graft Copolymers via ATRP as High-Performance NCM811 Cathode Binders

High-nickel layered oxides, e.g., LiNi0.8Co0.1Mn0.1O2 (NCM811), are promising candidates for cathode materials in high-energy-density lithium-ion batteries (LIBs). Complementing the notable developments of modification of active materials, this study focused on the polymer binder materials, and a new synthetic route was developed to engineer PVDF binders by covalently grafting copolymers from poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) with multiple functionalities using atom transfer radical polymerization (ATRP). The grafted random copolymer binder provided excellent flexibility (319% elongation), adhesion strength (50 times higher than PVDF), transition metal chelation capability, and efficient ionic conductivity pathways. The NCM811 half-cells using the designed binders exhibited a remarkable rate capability of 143.4 mA h g-1 at 4C and cycling stability with 70.1% capacity retention after 230 cycles at 0.5 C, which is much higher than the 52.3% capacity retention of nonmodified PVDF. The well-retained structure of NCM811 with the designed binder was systematically studied and confirmed by post-mortem analysis.

Imitating Architectural Mortise-Tenon Structure for Stable Ni-Rich Layered Cathodes

Ni-rich layered oxides are the most promising cathodes for Li-ion batteries, but chemo-mechanical failures during cycling and large first-cycle capacity loss hinder their applications in high-energy batteries. Herein, by introducing spinel-like mortise-tenon structures into the layered phase of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811), the adverse volume variations in cathode materials can be significantly suppressed. Meanwhile, these mortise-tenon structures play the role of the expressway for fast lithium-ion transport, which is substantiated by experiments and calculations. Moreover, the particles with mortise-tenon structures usually terminate with the most stable (003) facet. The new cathode exhibits a discharge capacity of 215 mAh g-1 at 0.1 C with an initial Coulombic efficiency of 97.5%, and capacity retention of 82.2% after 1200 cycles at 1 C. This work offers a viable lattice engineering to address the stability and low initial Coulombic efficiency of the Ni-rich layered oxides, and facilitates the implementation of Li-ion batteries with high-energy density and long durability.

Can the new energy vehicles (NEVs) and power battery industry help China to meet the carbon neutrality goal before 2060?

China is working to boost the manufacture, market share, sales, and use of NEVs to replace fuel vehicles in transportation sector to get carbon reduction target by 2060. In this research, using Simapro life cycle assessment software and Eco-invent database, the market share, carbon footprint, and life cycle analysis of fuel vehicles, NEVs, and batteries were calculated from the last five years to next 25 years, with a focus on the sustainable development. Results indicate globally, China had 293.98 m vehicles and 45.22% worldwide highest market share, followed by Germany with 224.97 m and 42.22% shares. Annually China's NEVs production rate is 50%, and sales account for 35%, while the carbon footprint will account for 5.2 E+07 to 4.89 E+07 kgCO2e by 2021-2035. The power battery production 219.7 GWh reaches 150%-163.4%, whereas carbon footprint values in production and use stage of 1 kWh of LFP 44.0 kgCO₂eq, NCM-146.8 kgCO₂eq, and NCA-370 kgCO₂eq. The single carbon footprint of LFP is smallest at about 5.52 E+09, while NCM is highest at 1.84 E+10. Thus, using NEVs, and LFP batteries will reduce carbon emissions by 56.33%-103.14% and 56.33% or 0.64 Gt to 0.006 Gt by 2060. LCA analysis of NEVs and batteries at manufacturing and using stages quantified the environmental impact ranked from highest to lowest as ADP > AP > GWP > EP > POCP > ODP. ADP(e) and ADP(f) at manufacturing stage account for 14.7%, while other components account for 83.3% during the use stage. Conclusive findings are higher sales and use of NEVs, LFP, and reduction in coal-fired power generation from 70.92% to 50%, and increase in renewable energy sources in electricity generation expectedly will reduce carbon footprint by 31% and environmental impact on acid rain, ozone depletion, and photochemical smog. Finally, to achieve carbon neutrality in China, the NEVs industry must be supported by incentive policies, financial aid, technological improvements, and research and development. This would improve NEV's supply, demand, and environmental impact.

Silver Nanocoating of LiNi0.8Co0.1Mn0.1O2 Cathode Material for Lithium-Ion Batteries

Surface coating has become an effective approach to improve the electrochemical performance of Ni-rich cathode materials. In this study, we investigated the nature of an Ag coating layer and its effect on electrochemical properties of the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode material, which was synthesized using 3 mol.% of silver nanoparticles by a facile, cost-effective, scalable and convenient method. We conducted structural analyses using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, which revealed that the Ag nanoparticle coating did not affect the layered structure of NCM811. The Ag-coated sample had less cation mixing compared to the pristine NMC811, which could be attributed to the surface protection of Ag coating from air contamination. The Ag-coated NCM811 exhibited better kinetics than the pristine one, which is attributed to the higher electronic conductivity and better layered structure provided by the Ag nanoparticle coating. The Ag-coated NCM811 delivered a discharge capacity of 185 mAh·g^-1 at the first cycle and 120 mAh·g^-1 at the 100th cycle, respectively, which is better than the pristine NMC811.

Air- and Moisture Robust Surface Modification for Ni-Rich Layered Cathode Materials for Li-Ion Batteries

The mainstream of high-energy cathode development is focused on increasing the Ni-ratio in layered structured cathode materials. The increment of the Ni portion in the layered cathode material escalates not only the deliverable capacity but also the structural degradation. High-Ni layered cathodes are highly vulnerable to exposure to air that contains CO₂ and H₂ O, forming problematic residual lithium compounds at the surface. In this work, a novel air- and moisture robust surface modification is reported for LiNi_0.8 Co_0.1 Mn_0.1 O₂ (NCM811) via the sol-gel coating method that selectively coats the internal surface area of the polycrystalline morphology secondary particles. Bare-, Li₂ SnO₃ -coated and LiCoO₂ -coated NCM811 are exposed to different ambient environments (air, hot-air, and moisture-air) to systematically investigate the correlation between the internal/external coating morphology and performance degradations. The LiCoO₂ -coated NCM811s exhibit high-capacity retention after exposure to all environments, due to the internal surface coating that prevents the penetration of harmful compounds into the polycrystalline NCM811. On the other hand, the Li₂ SnO₃ -coated NCM811s exposed to the ambient environments show gradual capacity fading, implying the occurrence of internal degradation. This paper highlights the impact of the internal degradation of polycrystalline NCM811 after environmental exposure and the correct coating mechanisms required to successfully prevent it.

Stabilizing the (003) Facet of Micron-Sized LiNi0.6Co0.2Mn0.2O2 Cathode Material Using Tungsten Oxide as an Exemplar

The structural stability of layered LiNi1-x-yCoxMnyO2 cathode materials is critical for guaranteeing their excellent electrochemical cycling performance, particularly at elevated temperatures. However, the notorious H2–H3 phase transition along with associated large changes in the c-axis or (003) facet is the fundamental origin of the anisotropic and abrupt change in the unit cell and the degradation of the cycling performance. In this study, we coat micron-sized LiNi0.6Co0.2Mn0.2O2 (NCM) with tungsten oxide via atomic layer deposition and investigate the atomic-to-microscopic structures in detail via advanced characterization techniques, such as Cs-corrected scanning transmission electron microscopy. The results reveal that coated tungsten oxide is predominately accumulated on the (003) facet of NCM, with the migration of a small amount of W6+ into this facet, resulting in a reduction of Ni3+ to Ni2+ and the formation of a rock-salt-like structure on the surface. The electrochemical cycling performance of tungsten-oxide-coated NCM is significantly improved, showing a capacity retention of 86.8% after 300 cycles at 55 °C, compared to only 69.4% for the bare NCM. Through further structural analysis, it is found that the initial tungsten-oxide-coating-induced (003) facet distortion effectively mitigates the expansion of the c-lattice during charge, as well as oxygen release from the lattice, resulting in a lowered strain in the cathode lattices and a crack in the cathode particles after prolonged cycling.

Layered Cathode Materials: Precursors, Synthesis, Microstructure, Electrochemical Properties, and Battery Performance

The exploitation of clean energy promotes the exploration of next-generation lithium-ion batteries (LIBs) with high energy-density, long life, high safety, and low cost. Ni-rich layered cathode materials are one of the most promising candidates for next-generation LIBs. Numerous studies focusing on the synthesis and modifications of the layered cathode materials are published every year. Many physical features of precursors, such as density, morphology, size distribution, and microstructure of primary particles pass to the resulting cathode materials, thus significantly affecting their electrochemical properties and battery performance. This review focuses on the recent advances in the controlled synthesis of hydroxide precursors and the growth of particles. The essential parameters in controlled coprecipitation are discussed in detail. Some innovative technologies for precursor modifications and for the synthesis of novel precursors are highlighted. In addition, future perspectives of the development of hydroxide precursors are presented.

Origin of the different degradation mechanisms of LNCM and LNCA cathodes in Li-ion batteries

Lithium nickel cobalt manganese oxide (LNCM) and lithium nickel cobalt aluminum oxide (LNCA) display similar performances and characteristics as cathode materials, but their degradation behaviors differ. To investigate the origin of these differences, the properties of LNCM and LNCA are comparatively examined computationally. Their structural, electronic, and transport properties show no significant differences, indicating that the degradation mechanisms cannot be explained through these intrinsic properties. Phase equilibria simulation shows that Mn embedment in the crystal is thermodynamically and kinetically favored; thus, the Mn concentration should be homogeneous over the LNCM particles. However, the Al distribution varies based on synthetic conditions, which can cause uneven concentration distributions or secondary-phase formation. In addition, the LNCA volume change with variations in Al concentration is more severe than that of LNCM with Mn concentration. Thus, LNCA particles may experience higher internal mechanical stresses, whereas the surfaces are protected by the secondary-phase coating effect. These features give LNCA robust surfaces but vulnerability to internal stress-induced particle breakage, while LNCM has relatively stable bulk properties but suffers surface-related degradation owing to bare surface exposure. This interpretation agrees well with the reported characteristic degradation behaviors of LNCM and LNCA, thus properly explaining the underlying mechanisms.

Improvement of the Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 via Atomic Layer Deposition of Lithium-Rich Zirconium Phosphate Coatings

Owing to its high energy density, LiNi_0.8Co_0.1Mn_0.1O₂ (NMC811) is a cathode material of prime interest for electric vehicle battery manufacturers. However, NMC811 suffers from several irreversible parasitic reactions that lead to severe capacity fading and impedance buildup during prolonged cycling. Thin surface protection films coated on the cathode material mitigate degradative chemomechanical reactions at the electrode-electrolyte interphase, which helps to increase cycling stability. However, these coatings may impede the diffusion of lithium ions, and therefore, limit the performance of the cathode material at a high C-rate. Herein, we report on the synthesis of zirconium phosphate (Zr_xPO_y) and lithium-containing zirconium phosphate (Li_xZr_yPO_z) coatings as artificial cathode-electrolyte interphases (ACEIs) on NMC811 using the atomic layer deposition technique. Upon prolonged cycling, the Zr_xPO_y- and Li_xZr_yPO_z-coated NMC811 samples show 36.4 and 49.4% enhanced capacity retention, respectively, compared with the uncoated NMC811. Moreover, the addition of Li ions to the Li_xZr_yPO_z coating enhances the rate performance and initial discharge capacity in comparison to the Zr_xPO_y-coated and uncoated samples. Using online electrochemical mass spectroscopy, we show that the coated ACEIs largely suppress the degradative parasitic side reactions observed with the uncoated NMC811 sample. Our study demonstrates that providing extra lithium to the ACEI layer improves the cycling stability of the NMC811 cathode material without sacrificing its rate capability performance.

Unveiling Sodium Ion Pollution in Spray-Dried Precursors and Its Implications for the Green Upcycling of Spent Lithium-Ion Batteries

Unclear impurity pollution is one of the key scientific problems that limit the large-scale production of new lithium-ion batteries (LIBs) from spent LIBs. This work is the first to report the pollution path, pollution degree, and solution method of sodium ions in the recycling process of spent LIBs in the real world. The results show that sodium ions can intrude into the precursor particles to form crystalline salts with the anion of the leaching acid that cover the transition metal elements, thereby resulting in a failed precursor. Specifically, the intrusion of sodium ions will produce a variety of pollutants containing metal oxide bonds, such as Na-O, NaO₂, and Na⁺-O₂, on the precursor surface. These active lattice oxygen will further adsorb or react to form organic oxygen, chemical oxygen, and free oxygen, which will highly deteriorate the surface cleanliness. Strictly controlling the consumption of sodium salt in each step and using ammonia instead of NaOH for pH regulation can effectively solve sodium ion pollution to prepare high-quality battery precursors. It reveals that for the green upcycling of spent LIBs, we should strengthen the design of the recycling process to reduce the consumption of chemical reagents, which will produce unexpected secondary pollution.

Rational Design of Effective Binders for LiFePO4 Cathodes

Polymer binders are critical auxiliary additives to Li-ion batteries that provide adhesion and cohesion for electrodes to maintain conductive networks upon charge/discharge processes. Therefore, polymer binders become interconnected electrode structures affecting electrochemical performances, especially in LiFePO4 cathodes with one-dimensional Li+ channels. In this paper, recent improvements in the polymer binders used in the LiFePO4 cathodes of Li-ion batteries are reviewed in terms of structural design, synthetic methods, and working mechanisms. The polymer binders were classified into three types depending on their effects on the performances of LiFePO4 cathodes. The first consisted of PVDF and related composites, and the second relied on waterborne and conductive binders. Profound insights into the ability of binder structures to enhance cathode performance were discovered. Overcoming the bottleneck shortage originating from olivine structure LiFePO4 using efficient polymer structures is discussed. We forecast design principles for the polymer binders used in the high-performance LiFePO4 cathodes of Li-ion batteries. Finally, perspectives on the application of future binder designs for electrodes with poor conductivity are presented to provide possible design directions for chemical structures.

Micron-Sized Monodisperse Particle LiNi0.6Co0.2Mn0.2O2 Derived by Oxalate Solvothermal Process Combined with Calcination as Cathode Material for Lithium-Ion Batteries

Ni-rich cathode LiNi_xCo_yMn_1-x-yO₂ (NCM, x ≥ 0.5) materials are promising cathodes for lithium-ion batteries due to their high energy density and low cost. However, several issues, such as their complex preparation and electrochemical instability have hindered their commercial application. Herein, a simple solvothermal method combined with calcination was employed to synthesize LiNi_0.6Co_0.2Mn_0.2O₂ with micron-sized monodisperse particles, and the influence of the sintering temperature on the structures, morphologies, and electrochemical properties was investigated. The material sintered at 800 °C formed micron-sized particles with monodisperse characteristics, and a well-order layered structure. When charged–discharged in the voltage range of 2.8–4.3 V, it delivered an initial discharge capacity of 175.5 mAh g⁻¹ with a Coulombic efficiency of 80.3% at 0.1 C, and a superior discharge capacity of 135.4 mAh g⁻¹ with a capacity retention of 84.4% after 100 cycles at 1 C. The reliable electrochemical performance is probably attributable to the micron-sized monodisperse particles, which ensured stable crystal structure and fewer side reactions. This work is expected to provide a facile approach to preparing monodisperse particles of different scales, and improve the performance of Ni-rich NCM or other cathode materials for lithium-ion batteries.

Temperature, Ageing and Thermal Management of Lithium-Ion Batteries

Heat generation and therefore thermal transport plays a critical role in ensuring performance, ageing and safety for lithium-ion batteries (LIB). Increased battery temperature is the most important ageing accelerator. Understanding and managing temperature and ageing for batteries in operation is thus a multiscale challenge, ranging from the micro/nanoscale within the single material layers to large, integrated LIB packs. This paper includes an extended literature survey of experimental studies on commercial cells investigating the capacity and performance degradation of LIB. It compares the degradation behavior in terms of the influence of operating conditions for different chemistries and cell sizes. A simple thermal model for linking some of these parameters together is presented as well. While the temperature appears to have a large impact on ageing acceleration above room temperature during cycling for all studied cells, the effect of SOC and C rate appear to be rather cell dependent.Through the application of new simulations, it is shown that during cell testing, the actual cell temperature can deviate severely from the reported temperature depending on the thermal management during testing and C rate. It is shown, that the battery lifetime reduction at high C rates can be for large parts due to an increase in temperature especially for high energy cells and poor cooling during cycling studies. Measuring and reporting the actual battery (surface) temperature allow for a proper interpretation of results and transferring results from laboratory experiments to real applications.